The present invention relates to an automatic take-up coupler. The coupler is adapted for maintaining two structural members in tension. The coupler of the present invention is connected to two elongated tension members and is designed to draw the two elongated tension members together where dimensional changes in the structures occur as in shrinkage of the wood materials.
The device is adapted for maintaining the tension forces between a pair of elongated tension members. The present invention is inserted between two elongated tension members and is designed to allow the ends of the two elongated tension members it connects to draw together, if conditions push the two proximal ends closer to each other or tension on the two ends is reduced.
The present invention is particularly suited for use with tie-down systems used to anchor wood-framed buildings to their foundations. Many such systems use a rod or bolt or an in-line series of rods or bolts that are anchored at their lower end to either a lower member of the building or directly to the foundation of the building. The upper ends of the bolt or rod or the series are connected to a plate or a bracket which, in turn, is connected to or rests upon an upper portion of the building. Intermediate portions or levels of the building may also be connected to the rod or the series of rods. Where the rod or series of rods is connected to the building, the rod or bolt is usually connected to the bracket by means of a nut thread onto the bolt or rod that presses against the plate or bracket. The rod or series of rods is placed in tension by tightening the nut against the plate or bracket that receives the rod or bolt and tensioning any coupling devices between the rods.
Tying elements of the building together with straps or cables is particularly intended to prevent damage or destruction to the building in the event of cataclysmic occurrences such as earthquakes, flooding or high winds. U.S. Pat. No. 573,452, granted Dec. 22, 1896, to Delahunt teaches the use of a standard turnbuckle to connect threaded rods that tie a building to its foundation.
For the rod or series of rods to serve as an effective anchor for the building it is important that the rod or series of rods remain in tension. However, a number of different factors can cause the tie-down system to lose its tension.
One such factor is wood shrinkage. Most lumber used in wood-frame construction has a water content when the building is constructed that is relatively high in comparison to the water content in the lumber after the building has been assembled. Once the envelope of the building is completed, the lumber is no longer exposed to the relatively humid outside air, and it begins to lose moisture which leads to shrinkage. A standard 2×4 can shrink by as much as 1/16″ of an inch across its grain within the first two years that it is incorporated in a building.
Delahunt '452 taught that as wood building structural members shrink during the life of the building, the cables will go slack and lose their ability to hold the wood members together. The turnbuckles that coupled the rods together in Delahunt '452 enabled workmen to hand rotate the turnbuckles to tighten the cables connecting the foundation and the roof or to connect wood roof members to other wood roof members. See also Williams, U.S. Pat. No. 5,664,389, granted Sep. 9, 1997, which uses non-adjustable clamps to couple multiple lengths of reinforcing bar to tie a roof structure of a multistory wood frame building to a concrete foundation.
In most wood frame structures, the cables and devices to tighten the cables, such as turnbuckles are buried within the structure after construction is completed. Manually turning the turnbuckles or other devices used to re-tension the cables is an expensive proposition particularly where building panels must be removed to reach the turnbuckles or other tightening devices.
Most of the wood shrinkage occurs during the first couple of years after construction but can continue at a much slower rate for several years. Since any loose connections in the building, during oscillating forces imposed on a building, such as during earthquakes, floods, and high wind, increase the probability of damage or destruction to the building, efforts have been made to tighten the connections by the use of automatic take-up devices.
A wide variety of methods have been proposed to automatically maintain the tension in anchoring rods and bolts used in tie down systems for buildings, so that an operator need not tighten them manually. See, for example: U.S. Pat. No. 5,180,268, granted to Arthur B. Richardson on Jan. 12, 1993; U.S. Pat. No. 5,364,214, granted to Scott Fazekas on Nov. 15, 1994; U.S. Pat. No. 5,522,688, granted to Carter K. Reh on Jun. 4, 1996; or U.S. Pat. No. 5,815,999, granted Oct. 6, 1998 to Williams. These devices are interposed between two work members and expand as the two members separate, maintaining the connection or contact between them. These devices are designed to expand without reversing or contracting once they are installed.
Another approach is taught by U.S. Pat. No. 4,812,096. This patent was granted to Peter O. Peterson on Mar. 14, 1989. In this method, the tension rods are pulled into connecting brackets as the building shrinks and settles, such that the over-all length of the tie-down system is reduced.
The present invention represents an improvement over the prior art methods. The present invention provides a novel take-up tension device that like Peterson '096 reduces the over-all length of the tie-down system as the tension in the in-line rod system attempts to reduce. The present invention is fully adjustable within a certain range of movement and provides a rigid force transmitting mechanism. Certain embodiments of the present invention also provide shielding for some of the working mechanisms of the device from the elements and dirt and grime.
The preferred coupler of the present invention is intended to be used in conjunction with holdowns and continuous tiedowns, as part of a restraint system in a wood or steel frame construction, to remove slack from the system by compensating for shrinkage and/or settlement of the framing. The preferred coupler of the present invention is an in-line coupling device that connects threaded rods together between storey levels, and maintains a tight configuration when shrinkage and/or settlement occurs. The device can be installed at any height in the wall, and is capable of compensating for up to one inch (25 mm) of shrinkage and/or settlement from the storey level above. Reducing couplers allow transitions between different rod diameters. Each end of the coupler is manufactured to create a positive stop for the threaded rod. The coupler has witness holes to allow for inspection of proper thread engagement.